#define   _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int single_dog_1(int arr[])
{
	int n = 0;
	for (int i = 0; i < 9; i++)
	{
		n ^= arr[i];
	}
	return n;
}
int main()
{
	int arr[] = { 1,2,3,4,5,1,2,3,4 };
	int n = single_dog_1(arr);
	printf("%d", n);

	return 0;
}